This invention is related to apparatus for examining an object by means of radiation such as x or gamma radiation. More particularly, the invention is concerned with tomographic rotational examination which enables two dimensional x-ray examination to represent the three dimensional configuration of a thin tomographic slice. Tomography has been employed to examine parts of the human body, such as the head, to ascertain the location of tumors and extraneous or foreign matter.
Some of the prior art tomographic devices provide for rotation of an x-ray source and x-ray detectors about the portion of the object being examined. Some of the prior art devices which utilize rotation employ cables which limit the extent of possible rotation, and thus necessitate the expenditure of time and effort by a technician to readjust or reposition the cables so that the x-ray process can be continued. Rotation may be limited to as little as 180.degree. in some devices. In other prior art devices, it is necessary for the x-ray technician or operator to manually adjust the position of the human body so that a different portion of the body can be x-rayed by a scan after a previous section has been scanned. Still other prior art devices have an x-ray source and x-ray detectors which are moved reciprocally relative to the body portion being examined, with their positions relative to the body portion being changed after each scan is taken.
Prior art devices have also taken x-ray slices of thicknesses of eight millimeters or greater. The thicknes of prior slices made it difficult to detect pathological tissue or other irregularities in tissue structure. It is difficult to compensate for the great amount of normal tissue included in a slice of eight millimeters thickness when the data from the slice is analyzed. As a result, displayed representations of the slice, either visual or numerical, are not entirely satisfactory. The averaged normal tissue tends to obscure the presence of abnormal structure.
The present device has considerable advantages over the prior art. The new device is continuously rotatable in one direction. Consequently there is no need to reposition or readjust cables for each rotation and the examination proceeds considerably faster. In addition, the subject is automatically repositioned with each complete rotation so an examination sequence of several rotations and examination "slices" can be conducted in sequence continuously. The x-ray source is pulsed many times as the x-ray source and detector are rotated around the subject. Each pulse constitutes an examination of the subject. One rotation of the device then provides a great quantity of data which can be analysed to provide a more accurate model of the examined subject. The x-rays are projected in a thin beam, allowing greater discrimination between observed structure, as described in the reference Neurological CAT System by Artronix Incorporated, incorporated herein by reference.
Even with the thinner scan, the time of a complete examination sequence for a subject such as a human head is considerably reduced. The time for each scan is reduced due to the continuous mode of operation of the device and the pulsed series of examinations in each rotation. The subject is automatically indexed forward at the completion of each rotation of the device and a new scan proceeds. As a result of the increased speed per scan and the increased speed between scans in a sequence, the total examination time for a subject is greatly reduced, with greater accuracy. As a result a tomograph machine can be used to examine more subjects, such as human patients, per day with less cost in capital investment and labor per examination.